The present disclosure relates to airflow control devices for vehicles, and more particularly, to reversibly deployable air dams for vehicles that use active materials to effect deployment and retraction.
Airflow over, under, around, and/or through a vehicle can affect many aspects of vehicle performance including vehicle drag, vehicle lift and down force, and cooling/heat exchange for a vehicle power train and air conditioning systems. Reductions in vehicle drag improve fuel economy. Vehicle lift and downforce can affect vehicle stability and handling. As used herein, the term “airflow” refers to the motion of air around and through parts of a vehicle relative to either the exterior surface of the vehicle or surfaces of elements of the vehicle along which exterior airflow can be directed such as surfaces in the engine compartment. The term “drag” refers to the resistance caused by friction in a direction opposite that of the motion of the center of gravity for a moving body in a fluid. The term “lift” as used herein refers to the component of the total force due to airflow relative to a vehicle, acting on the vehicle in a vertically upward direction. The term “downforce” used herein refers to the component of total force due to airflow relative to the vehicle acting on a vehicle in a vertically downward direction.
Devices known in the art of vehicle manufacture to control airflow relative to a vehicle are generally of a predetermined, non-adjustable geometry, location, orientation and stiffness. Such devices generally do not adapt as driving conditions change, thus the airflow relative to the vehicle cannot be adjusted to better suit the changing driving conditions. Additionally, current under-vehicle airflow control devices can reduce ground clearance. Vehicle designers are faced with the challenge of controlling the airflow while maintaining sufficient ground clearance to avoid contact with and damage by parking ramps, parking blocks, potholes, curbs and the like. Further, inclement weather, such as deep snow, slush or rainfall, can damage the device and/or impair vehicle handing.
Current stationary airflow control devices may be adjustable by mounting and/or connecting the devices to hydraulic, mechanical, electrical actuators and/or the like. For example, some vehicle airflow control devices may adjust location and/or orientation in response to an actuator signal. However, such actuators generally require additional components such as pistons, motors, solenoids and/or like mechanisms for activation, which increase the complexity of the device often resulting in increased failure modes, maintenance, and manufacturing costs. Therefore, there exists a need for an adjustable device for controlling vehicle airflow under varying driving conditions that enhances device simplicity while reducing device problems and the number of failure modes.
There are many general types of airflow control devices used for vehicles, two of these are air dams and spoilers. FIG. 1 illustrates a vehicle 1 that includes an air dam 3 and a spoiler 5 in locations typically associated with their functions as discussed below. Air dams differ from spoilers in terms of form, functionality, placement, and design. Air dams can generally be defined as frontal airflow restrictors designed to smooth the flow of air around (under) a vehicle, decreasing the coefficient of drag, improving fuel economy, handling, and maneuvering at high speeds. In contrast, a spoiler is designed to improve traction by increasing the downward force on the rear portion of a vehicle. The use of spoilers increases the cornering capability and improves stability at high speeds, but often at the expense of additional aerodynamic drag and weight.
Current air dams and spoilers are generally of a fixed geometry, location, orientation, and stiffness. Such devices can thus not be relocated, reoriented, reshaped, etc. as driving conditions change and thus airflow over/under/around the vehicle body can not be adjusted to better suit the changed driving condition. Also, current air dams reduce the vehicle's ground clearance, and thus presents a constant challenge to designers to provide the needed control of airflow while maintaining sufficient ground clearance to avoid contact with and being damaged by parking ramps, parking blocks, and encounters with potholes and curbs. Along these lines underbody airflow control devices, if they extend sufficiently close to the ground, can present a problem with regards to driving through deep standing water, slush, snow, and off-road unpaved surfaces.
Accordingly, it would be desirable to have a deployable air dam that can be selectively deployed and retracted according to the driving conditions.